Field
Embodiments of the present disclosure generally relate to a reflector for use in thermal processing chambers.
Description of the Related Art
Rapid thermal processing (RTP) and epitaxial deposition (epi) systems are employed in semiconductor chip fabrication to create, chemically alter or etch surface structures on semiconductor substrates. RTP and epi systems typically depend upon an array of high-intensity incandescent lamps fit into a lamphead and directed at the substrate. The lamps are electrically powered and can be very quickly turned on and off and a substantial fraction of their radiation can be directed to the substrate. As a result, the substrate can be very quickly heated without substantially heating the chamber and can be nearly as quickly cooled once the power is removed from the lamps.
The thermal processing chamber may include, among other components, an upper structure, a lower structure, a base ring connecting the upper structure to the lower structure, a rotating substrate support disposed between the upper structure and the lower structure, a lamphead positioned proximate to the lower structure, and a reflector positioned proximate to the upper structure. A number of infrared lamps are located in the lamphead. The lamps are divided into multiple zones. Each zone is separately powered by a lamp driver that is, in turn, controlled by a multi-input, multi-output controller. During processing, radiation from the lamps radiates through the lower structure and onto a substrate placed on the substrate support. In this manner, the substrate is heated to a required processing temperature.
However, it has been observed that radiation from the lamps can bypass the substrate and the substrate support, and radiate onto the reflector and optical pyrometers associated with the reflector. The radiation from the lamps thus creates error (also known as noise) in the pyrometry reading for the substrate, resulting in inaccurate temperature measurement. In addition, not all of the electrical energy delivered to the lamps ends up actually heating the wafer. Some of the radiant energy is absorbed by chamber components, which causes the chamber to cool down undesirably slow and therefore, longer step change times and slower process throughput.
Thus, there is a need in the art for an apparatus which enables more accurate temperature measurement and faster chamber cooling.